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Copyright 1996, 2000, Denis Cousineau

2. Making a computer controlled robotic arm

Circuitry information

In order to create the circuitry below, you need a computer software that will control your parallel port. (see
Program button above). If you are not very familiar with electronic, I *STRONGLY* recommend that you buy an old cheap parallel port card –or even an old computer– , just in case you make a short-circuit. It happen to me twice...

You need to buy a few electronic pieces, described in a drawing and pictured in here. Also needed are a few mounting pieces, pictured here. It will cost you about 30 US$. For example, a transistor (model number 2N2222) costs ~50˘, a DPDT relay, ~1.75$ (this is maybe the most expensive piece, you need 7).

Schematic

The schematic uses a DPDT relay to implement a H-bridge for bi-directional control of one DC-motor.

Component side and trace side

This implementation uses IC-sockets to hold the pieces. That way, they are not soldered and can be replaced easily. Instead of two 18-pin sockets, you could use 10- and a 18-pin sockets.

Component list

RL1

Relay

DPDT

T1, T2

Transistors

2N2222 (NPN)

BR1, BR2, BR3, BR4, BR5

Bridge

(wire)

IC-Socket

18-pin

R1, R2

Resistors

1 K ohms

ST1 to ST6

Connectors

One- and two pins

Connection list

ST1

Direction

Pin #8 of DB25 cable

ST2

Ground

power supply

ST3

Power

+9v

ST4

On/Off

Pin #2 of DB25 cable

ST5

To device

Motor

ST6

Ground

Pin #25 of DB25 cable

Look at the Tutorials for more information.

With this circuit, you'll be able to control up to 7 motors, and their direction of motion.